The evaluation of a neutropenia first must document its etiology. Besides the particular etiological aspects in the newborn, neutropenia in a child may be 1) acquired, 2) constitutional, part of a complex genetic disease, 3) constitutional, isolated. Primary acquired neutropenia, also called benign chronic neutropenia, is the most frequent cause of chronic neutropenia in children; it is usually well tolerated and has a frequent favorable outcome in 12-14 months. Many complex genetic diseases include a neutropenia, among which several immunologic disorders that must be ruled out before considering the diagnosis of isolated constitutional neutropenia. Infantile agranulocytosis is the main primary constitutional neutropenia. It may be sporadic or hereditary (autosomal recessive or dominant inheritance) and is present at birth. It is profound, usually < 0.5 G/l (< 500/mm3) and exposes to severe pyogenic and fungal infections. In the neonatal period neutropenia must primarily suggest a bacterial infection, although other etiologies have to be known, particularly neonatal neutropenia caused by passive transfer of maternal antibodies and neutropenia related to gravidic maternal hypertension. The treatment of severe chronic neutropenia is directed towards the prevention of infections. It includes prophylactic antibiotherapy, the most commonly used one being the trimetroprim-sulfamethoxazole association, and granulocyte colony stimulating factor (G-CSF). G-CSF has considerably improved the condition of patients; it is usually well tolerated, but secondary effects have been reported (hypersplenism, glomerulonephritis, osteoporosis, vasculitis), and a potential leukemogenic risk has been evoked.